Paper No. 8
Presentation Time: 10:40 AM
MIRROR IMAGE LATE QUATERNARY SPELEOTHEM OXYGEN ISOTOPIC RECORDS FROM CAVES IN SOUTHERN BRAZIL AND EASTERN CHINA
We have obtained a high resolution oxygen isotopic record of cave calcite from Caverna Botuverá (27°13'S, 49°09'W), southern Brazil. The chronology was determined by ~ 80 high-resolution U/Th ages from 5 stalagmites. Tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change. We interpreted our record, spanning the last 90 kyr, in terms of meteoric precipitation changes at this low-latitude location. The oxygen isotopic profile broadly follows local insolation changes and shows clear millennial-scale variation during the last glacial period with amplitudes as large as 3 per mil but with much smaller shifts (< 1 per mil) during the Holocene. This pattern is very similar to (but anti-correlated with) some Northern Hemispheric observations (e.g., Wang et al., 2001, Science; Bar-Matthews et al., 2003, GCA; Burns et al., 2003, Science; Fleitmann et al., 2003, Science; Gomez et al., 2003, GSA abstract; Yuan et al., 2004, Science).
Using independent age scales, we compare our record to contemporaneous records from Hulu Cave (Wang et al., 2001) and Dongge Cave (Yuan et al., 2004), eastern China. Minima in d18O (wet periods) at our site are synchronous with maxima in d18O (dry periods) in eastern China and vice versa. This anti-phased precipitation relationship between two low-latitude locations may be related to asymmetry in Hadley cell circulation in two hemispheres, associated not with seasonal changes as observed today, but with millennial-scale climate shifts. If southern Brazil and eastern China records are broadly representative of low-latitude rainfall in their respective hemispheres, and if rainfall is directly related to absolute humidity, then the atmospheric see-saw pattern that we observe could have important consequences because of water vapor's greenhouse properties.